1. Field of the Invention
The present invention relates generally to a fluid-filled elastic mount, and more particularly to improved construction of such a fluid-filled elastic mount adapted to prevent or minimize vibrations or booming noises due to resonance of a mounting bracket or a similar member for mounting the elastic mount.
2. Discussion of the Prior Art
An elastic mount is known as a vibration damping device interposed between two members of a vibration system, for flexibly connecting these two members. As one type of such elastic mount, there is known a so-called fluid-filled elastic mount as disclosed in laid-open Publication No. 57-9340 of unexamined Japanese Patent Application, which includes a first and a second rigid support member that are radially spaced apart from each other by a suitable distance, an elastic body interposed between these first and second support members to elastically connect the two support members, and a partition structure which is supported by the second support member and which partially defines a pressure-receiving chamber and an equilibrium chamber on the opposite sides thereof. These chambers are filled with a non-compressible fluid. The pressure-receiving chamber is partially defined by the elastic body, so that the pressure of the fluid in the pressure-receiving chamber changes due to elastic deformation of said elastic body, upon application of a vibrational load to the elastic mount. The equilibrium chamber is partially defined by a flexible diaphragm, so that the volume of the equilibrium chamber is easily variable. The pressure-receiving and equilibrium chambers communicate with each other through an orifice passage, so that the fluid is permitted to flow through the orifice passage between the two chambers when the pressure in the pressure-receiving chamber changes. In this type of fluid-filled elastic mount, a cap member is attached to the second support member by calking or other suitable means, for protecting the flexible diaphragm.
The fluid-filled elastic mount constructed as described above is capable of providing an excellent vibration damping or isolating effect which cannot be obtained by the elasticity of an elastic body alone, based on resonance of the fluid flowing through the orifice passage. Thus, the fluid-filled elastic mount of this type has been suitably used as an engine mount for a motor vehicle, for example.
Such a fluid-filled elastic mount is installed between two members to be flexibly connected, such that the first rigid support member is fixed to one of these two members while the second rigid support member is fixed to the other of the two members. Depending upon the construction or configuration of the two members to be flexibly connected by the elastic mount, a suitable mounting bracket is attached to the second support member, so that the second support member is fixed to the appropriate member through the mounting bracket.
The mounting bracket is usually formed from a steel plate by pressing, and tends to resonate at the frequency of the vibration received by the elastic mount, causing booming noises. Further, the resonating mounting bracket results in amplifying the received vibration, whereby the damping function of the elastic mount may be deteriorated or adversely influenced.
One possible solution to the problem indicated above is to attach a dynamic damper directly to the mounting bracket. Where the elastic mount is used as the engine mount for motor vehicles, however, it is difficult in most cases to provide the mounting bracket with an effective damping mechanism, because of a limited installation space allocated to the engine mount. Moreover, the provision of such a damping mechanism for the mounting bracket requires additional parts or components, vulcanization process and assembling steps other than those for the elastic mount per se, whereby the cost of manufacture of the elastic mount assembly including the mounting bracket and dynamic damper is inevitably increased. Therefore, the solution is not found effective to deal with the problem with the mounting bracket.